ImmunoGen, Inc. (Nasdaq: IMGN), a biotechnology company that develops novel anticancer therapeutics using its antibody-drug conjugate (ADC) technology, today announced positive decisions for Kadcyla (trastuzumab emtansine, formerly T-DM1) in both the European Union (EU) and Japan, the two largest pharmaceutical markets after the US. Kadcyla was approved for marketing in the US earlier this year.

The EU’s Committee for Medicinal Products for Human Use (CHMP) has recommended approval of Kadcyla for the treatment of adults with HER2-positive, inoperable locally advanced or metastatic breast cancer who previously received trastuzumab and a taxane, separately or in combination. This decision is based on the findings in the EMILIA Phase III trial. A decision by the European Commission is expected by year end. An approval decision would trigger a $5 million milestone payment to ImmunoGen.

The Japanese Ministry of Health, Labor and Welfare (MHLW) has approved Kadcyla for the treatment of inoperable or recurrent HER2-positive breast cancer based on results from a Japanese Phase II trial and the EMILIA Phase III trial. This event triggers a $5 million milestone payment to ImmunoGen.

“These positive decisions are important steps toward Kadcyla becoming available for patients in the EU and Japan,” commented Dan Junius, President and CEO.

The EMILIA trial assessed Kadcyla compared to standard therapy for the treatment of patients with HER2-positive metastatic breast cancer who had previously received Herceptin ® (trastuzumab) and a taxane. Kadcyla demonstrated a significant improvement in overall survival and in progression-free survival, and fewer patients experienced severe adverse events, compared to standard therapy.

Kadcyla consists of Roche’s trastuzumab antibody and ImmunoGen’s DM1 cytotoxic agent. The DM1 is attached to the antibody using one of ImmunoGen’s linkers. Roche has global development and commercialization rights for Kadcyla; ImmunoGen is entitled to receive specified milestone payments and royalties on product sales.

Roche is conducting a number of studies assessing Kadcyla for potential additional uses. These include for the first-line treatment of HER2-positive metastatic breast cancer, for early stage HER2-positive breast cancer and for advanced HER2-positive gastric cancer.

About ImmunoGen, Inc.

ImmunoGen, Inc. develops targeted anticancer therapeutics. The Company’s ADC technology uses a tumor-targeting engineered antibody to deliver one of ImmunoGen's highly potent cancer-cell killing agents specifically to tumor cells. The most advanced compound with ImmunoGen's ADC technology is Roche’s Kadcyla, which is marketed in the US by Genentech. ImmunoGen has four wholly owned clinical-stage product candidates, with additional compounds in the clinic through its partnerships with Amgen, Bayer HealthCare, Biotest and Sanofi. More information about the Company can be found at www.immunogen.com.

Kadcyla ® and Herceptin ® are registered trademarks of Genentech, Inc., a member of the Roche Group.

This press release includes forward-looking statements. For these statements, ImmunoGen claims the protection of the safe harbor for forward-looking statements provided by the Private Securities Litigation Reform Act of 1995. It should be noted that there are risks and uncertainties related to the development of novel anticancer products, including risks related to regulatory decisions, their timings and results. A review of these risks can be found in ImmunoGen’s Annual Report on Form 10-K for the fiscal year ended June 30, 2013 and other reports filed with the Securities and Exchange Commission.